1. Field of the Invention
The present invention relates to a resin sheet suitable for use in thermoforming, and to a thermoformed article and multilayer structure which are obtained from the resin sheet.
2. Description of the Related Art
In the production of formed articles, especially injection molded articles, made of thermoplastic resin for use in the fields of automobiles and household appliances, a method for producing formed articles of excellent surface appearance includes a method comprising setting a resin sheet such as that described in WO88/07416 (this may be called a xe2x80x9cpaintless filmxe2x80x9d) into a mold for molding resin and then supplying a thermoplastic resin into the mold, thereby shaping the thermoplastic resin and at the same time laminating the resin to the resin sheet. In the practice of that method, the resin sheet is often shaped into a designed form by thermoforming such as vacuum forming, etc. before its setting into the mold.
In general, the resin sheets used for such a purpose is roughly classified, in view of their production method, into those produced by cast processing (e.g., those described in WO88/07416, JP-A-11-20789, etc.) and those produced by T-die processing (e.g., those described in JP-A-10-279766). Desired are those produced by T-die processing because of costs.
Resin sheets used as paintless films usually comprise a transparent layer, a design layer and a backing layers. For the transparent layer, poly(methyl methacrylate) is often used for simultaneous achievement of highly glossy appearance and high scratch resistance. Use of polyolefin resins, which are less expensive than poly(methyl methacrylate) and are of good recyclability, have also been demanded recently.
However, the conventional resin sheets produced by T-die processing from poly(methyl methacrylate), polyolefin resins or the like have a problem in that minute irregularities are formed in their surfaces after their thermoforming. Under such circumstances, the object of the present invention is to provide a resin sheet in a surface of which no minute irregularities are formed during or after its thermoforming and which is easy to handle during its thermoforming, and to provide a thermoformed article and multilayer structure having no minute irregularities in surfaces thereof.
The aforementioned object has been attained mainly by the following creations (1), (2) and (3):
(1) A resin sheet comprising a resin layer that comprises a thermoplastic resin and that has a degree of orientation of not less than 0.0002 and not more than 0.0020.
(2) A thermoformed article which is obtained by thermoforming the resin sheet according to item (1).
(3) A multilayer structure comprising a thermoformed article and a substrate multilayerd to the thermoformed article, the thermoformed article being obtained by thermoforming the resin sheet according to item (1) and the substrate comprising a thermoplastic resin.
A film and a sheet are generally distinguished from one another base on their thickness. However, in the present invention, films and sheets are defined generically as xe2x80x9csheetsxe2x80x9d.